Obesity is currently one of the major epidemics, representing an important public health problem that is associated with an increase in chronic disease. The scope of this study is to investigate the prevalence of excess weight and obesity and associated factors in 20 to 59-year-old women attended at First Aid Units of the Unified Health System. Standardized interviews and anthropometric measurements were conducted with 440 women. Factors associated with the presence of excess weight/obesity were investigated using the Poisson model with robust variance. The prevalence of excess weight and obesity (64.3%) as well as central obesity (44.1%) in women attended at First Aid Units is higher than that in the population in general and is associated with an increased incidence of health problems. Insufficient physical activity (PR=1.44; 95% CI 1.24-1.66), a history of three pregnancies or more (PR=1.45; 95% CI 1.05-2.00), age above 50 (PR=1.34; 95% CI 1.00-1.82) and central obesity (PR=1.92; 95% CI 1.64-2.25) are associated with a higher prevalence of obesity. The implementation of public health polices focused on the prevention of obesity would undoubtedly have a major impact on primary prevention of chronic diseases in the female population.